GSLC sigma0, beta0, and gamm0 LUTs cover additional area

[nemo794]

In GSLC products CRID 05023 (and maybe earlier?), the sigma0, beta0, and gamm0 LUTs cover additional area significantly beyond the extent of the radar swath, extending through the lower-right corner of the LUTs.

Two example granules which illustrate this.

1) NISAR_L2_PR_GSLC_025_135_A_024_4005_DHDH_A_20260717T131933_20260717T131941_P05023_N_P_J_001

2) NISAR_L2_PR_GSLC_025_119_A_025_2005_QPDH_A _20260716T104158_20260716T104233_P05023_N_F_J_001

cc: @hfattahi @seongsujeong @gshiroma

[seongsujeong]

I think that is intended behavior to ensure that the valid area is covered by the LUT.